Flow rate adjusting device

ABSTRACT

The invention relates to a flow control device which comprises at least two control disks which are arranged coaxially with respect to one another, lie tightly against one another and can rotate relative to one another about their common axis, the control disks having a through-bore arranged eccentrically and leading through in the axial direction, and, on the side faces lying against one another, in each case a recess which, starting from the through-bore, extends along an arc of a circle about the axis of the control disks, so that if there is relative rotation, only parts of the opposite recesses overlap.

The invention relates to a flow control device, in particular forliquids.

The object of the invention is to design a flow control device in such away that the flow path and also the flow rates can be adjusted.

According to the invention, this object is achieved by the features inclaim 1. By virtue of the fact that the recesses extending laterallyfrom the through-bores in the adjacent side faces of the disks, whichcan rotate relative to one another, are able to overlap to differentextents, it is possible, for example, starting from a maximum flow ratewith the through-bores flush, to adjust to very low flow rates as aresult of the terminal points of the tapering recesses overlappingslightly. In this way, flow rates can be adjusted steplessly to therange of microliters to nanoliters.

Illustrative embodiments of the invention are explained in more detailbelow with reference to the drawing, in which:

FIG. 1 shows a perspective view of a flow control device with controlunit,

FIG. 2 shows a diagrammatic longitudinal section through an embodimentof the flow control device with a plurality of control disks,

FIG. 3 shows a perspective view of a stationary control disk,

FIG. 4 shows a perspective view of a rotatable control disk,

FIG. 5 shows the securing of a rotatable control disk on a wormwheel,

FIG. 6 shows a sectional view through a drive means of the wormwheel,and

FIG. 7 shows a modified embodiment of a control disk.

In FIG. 1, reference number 1 indicates the flow control device throughwhich a liquid flows in the axial direction, indicated by the arrows Xand Y. Arranged on the housing 2 of the flow control device, via anattachment 2′, there is a coupling and sealing adapter 3 on which amotor housing 4 is secured, in which for example a direct-current motoror a linear motor is arranged. A control unit 5 with electronic controlmeans is arranged on the motor housing 4.

FIG. 2 shows diagrammatically a longitudinal section through the flowcontrol device 1. A screw-on sleeve 6 with a threaded portion 6′ isscrewed onto the tubular section 2″ of the housing 2, which screw-onsleeve 6, together with a separately formed threaded portion 6″, holds ahousing part 7 bearing on the tubular housing section 2″. Referencenumber 8 indicates a seal, for example an O-ring between the two housingparts 2 and 7. The threaded portion 6′ is for example designed as aright-hand thread, while the threaded portion 6″ is designed as aleft-hand thread. In this way, the two housing parts 2 and 7 can befixed by the screw-on sleeve 6 so as to bear tightly on one another.

Inserted into a central bore of the housing part 7 there is a fixedplug-in shaft 9 which, on the circumference, has a serrated profile or atoothing which engages with a corresponding serrated profile in thehousing bore. In the illustrative embodiment shown, nine control disks10 to 18 are arranged on this plug-in shaft 9. The first control disk 10and the control disk 18 at the opposite end are fixed in a stationaryposition on the plug-in shaft 9 via the serrated profile, and likewisethe control disks 12, 14 and 16, whereas the intermediate control disks11, 13, 15 and 17 are rotatable on the plug-in shaft 9 as a result of agreater diameter of the bore. The control disks 10 to 18 are held lyingtightly against one another by means of the pretensioning of a cupspring 19 which is arranged in a recess of the housing 2. The controldisks 10 to 18 are surrounded by a sleeve-shaped wormwheel 21 which canbe set in rotation by a worm shaft 22 which, as is shown in FIG. 6, isrotated by the drive motor arranged in the motor housing 4. Therotatable control disks 11, 13, 15 and 17 are each connected to thewormwheel 21, whereas the stationary control disks 10, 12, 14, 16 and 18can slide on the inner circumference of the sleeve-shaped wormwheel 21or can also have an external diameter smaller than the internal diameterof the sleeve-shaped wormwheel 21. In the illustrative embodiment shown,the rotatable control disks are connected to the wormwheel 21 free fromplay via a centering grub screw 23, as is shown in FIG. 5. Here, forexample, four wedge-shaped carrier grooves 24 are formed on the outercircumference of a rotatable control disk (FIG. 4), into which grooves24 the wedge-shaped point of the centering grub screw 23 engages. Thesecentering grub screws are provided with a hexagon socket, as isindicated in FIG. 5.

In the area of the control disk 17, the sleeve-shaped wormwheel 21 has,on the outer circumference, a worm thread 20 which engages with thethread of a worm shaft 22. The sleeve-shaped wormwheel 21 is mountedrotatably in both housing parts 2 and 7 via slide bearings 26 at theopposite ends.

A seal 27 is provided in each case on the end faces of the two housingparts 2 and 7 and bears on the side faces of the stationary disks 10 and18. Both housing parts 2 and 7 are each provided with an attachmentpiece 28 with external thread and a flanged cone 29 for flangedscrewing-on of an attachment hose 52. The hose 52 or a bundle-tube isconnected in a sealed manner to the attachment piece 28 via a rivet nut51.

The control disks 10 to 18 are each provided with a through-bore 30which is arranged eccentrically on the individual control disks in theaxial direction, as FIGS. 3 and 4 show. Arranged on the stationarycontrol disk 10, on one side face 32 of the control disk, there is arecess 31 which, starting from the through-bore 30, arranged at adistance r from the axis, tapers off in width and depth and extends inan arc of a circle about the axis at the distance r from said axis. Inthe illustrative embodiment shown in FIG. 3, this tapering recess 31extends almost in a semicircle about the axis on the side face 32. Theopposite side face of the control disk 10 is smooth and is provided onlywith the through-bore 30.

FIG. 4 shows a rotatable control disk, for example the control disk 11.Formed on the side face 33 of the rotatable control disk 11 lyingopposite the side face 32 of the stationary control disk 10, there is arecess 31 a which tapers off starting from the through-bore 30 almostabout a semicircle and is identical in design to the recess 31 on thecontrol disk 10, but extends in the opposite direction. While the recess31 on the control disk 10 extends in the clockwise direction startingfrom the through-bore 30, the recess 31 a on the opposite side face 33of the control disk 11 extends in the opposite direction so that, uponalignment of the through-bores 30, the one recess 31 a extends in theclockwise direction and the recess 31 on the opposite control diskextends in the anticlockwise direction about the axis. By rotating thecontrol disk 11 relative to the control disk 10, the passage crosssection can be decreased continuously along the recesses 31 and 31 auntil only the terminal points of the two recesses 31 and 31 a overlapslightly, so that only a minimal passage cross section remains.

On the side face opposite from the side 33, the rotatable control disk11 has a corresponding recess 31 b which starts from the through-bore30, as shown by broken lines in FIG. 4. The recess 31 b extends in theopposite direction to that on the side face 33 and in the same directionas the recess 31 on the control disk 10.

Correspondingly, the stationary control disk 12 is designed with arecess 31 a and 31 b tapering along an arc of a circle on both sidefaces. In terms of the arrangement and design of the recesses 31 a and31 b, the control disks 11 to 17 are of identical design, the respectiverecesses tapering off continuously in width and depth along the arc of acircle. The stationary control disk 18 at the opposite end has amirror-inverted design in relation to the control disk 10, with a recess31 on only one side face.

In FIG. 2, the through-bores 30 of all the control disks 10 to 18 arerepresented in a flush position, so that there is a through-channel witha minimal diameter corresponding to that of the bores 30. A passagechannel 35 starting from the attachment piece 28 extends in a curvedconfiguration through the housing parts 2 and 7 in such a way that it isflush with the eccentric through-bore 30 of the control disks 10 and 18.In one illustrative embodiment, the internal diameter of the passagechannel 35 and the internal diameter of the through-bores 30 can be 5mm, for example, the recesses 31 tapering off continuously in width anddepth to zero starting from the through-bores 30.

The rotatable control disks 11, 13, 15 and 17 are rotated in synchronyrelative to the stationary control disks 10, 12, 14, 16 and 18 by thewormwheel 21, so that, between the side faces of the individual controldisks lying against one another, the same passage cross sectioncorresponding to the overlapping of the recesses 31, 31 a, 31 b etc.occurs.

By means of this succession of reduced passage cross sectionscorresponding to throttle positions, a high pressure of the liquidentering at the inlet side at X can be reduced in steps at theindividual throttle positions as far as the outlet at Y. By means of thethrottle positions arranged one behind the other, differential pressuresof 2 to 300 bar can be reduced in steps, and very low flow rates in therange of microliters and nanoliters are also possible.

When the control disks are rotated relative to one another from the viewin FIG. 2, so that throttle positions are formed by cross-sectionalreduction at the overlapping recesses 31, 31 a, 31 b, etc., channelportions of enlarged cross section form between the individual throttlepositions because the liquid leaving one throttle position flows throughthe full cross section of a through-bore 30 before it comes to the nextthrottle position. In this way, a staged throttle is obtained, withexpansion between the throttle positions, for pressure reduction.

Such a flow control device can be used in biotechnology, in finechemistry and in various fields of application.

Instead of the nine control disks provided in the illustrativeembodiment shown, a smaller number of control disks or a larger numbercan also be provided. For example, it is also possible to provide justone rotatable control disk between the stationary control disks 10 and18.

The control disks can be made of ceramic material or else of a syntheticsuch as Teflon, the side faces which lie against one another being madesmooth so that they lie tightly against one another under thepretensioning of the cup spring 19. Moreover, pressure compensationchannels (not shown) can be provided on the individual control disks inorder to compensate for the pressure acting in the axial direction ofthe flow control device.

The central bore 34 on the rotatable control disks 11, 13, 15 and 17 hasa diameter which is equal to or slightly greater than the externaldiameter of the toothing on the plug-in shaft 9, so that these rotatablecontrol disks can be easily rotated on the plug-in shaft. By means ofthe wedge-shaped carrier grooves 24, a clearance-free adjustment of therotatable control disks is possible with the wormwheel 21 via thecentering grub screws 23.

In the orientation of the through-bores 30 corresponding to therepresentation in FIG. 2, that is with a continuously full crosssection, a washing liquid can flow through the device, it being alsopossible for a ball to be passed through the flow control device inorder to clean the passage channels.

FIG. 6 shows diagrammatically an example of a means for driving thewormwheel 21 via the worm 22, which is mounted rotatably in theattachment 2′ of the housing. In the illustrative embodiment shown, awobble rod 40 is arranged between the worm 22 and a shaft 41 mounted inthe housing attachment 2′, and is guided through a stiff membrane 42which on the one hand forms an articulation point for the wobble rod 40and on the other hand seals the housing off from the drive unit.

Reference number 43 indicates a radial slide bearing for the worm 22which at the opposite end bears on an axial bearing 44 and isadditionally mounted in the housing via a radial bearing 45. Referencenumber 46 indicates a spacer ring between the axial bearing 44 and aring 47 which holds the membrane 42 and, on the outer circumference, issealed off from the housing by a seal, for example an O-ring 48.

A sealing shim (not shown) and a corresponding bearing can be providedon the shaft 41.

As FIG. 1 shows, viewing windows 50 can be provided on the coupling andsealing adapter 3, through which windows 50 the sealing of the flowcontrol device in relation to the drive unit can be monitored.

The flow control device described forms a micro-dosing fixture by meansof which it is also possible to control very low flow rates.

According to a further embodiment of the invention, the lateral recesses31 can, depending on the field of application of the flow controldevice, also have a shape other than that shown in which the width anddepth of the recess 31 taper to zero starting from the through-bore 30.Thus, for example, in the overlapping state, the recesses can form aflow cross section which corresponds to that of the through-bores 30, sothat by rotating the control disks relative to one another, startingfrom a position in which the through-bores 30 are flush with one anotherand form the shortest flow distance through the device, the flow paththrough the device can be lengthened by means of a channel which extendsin the circumferential direction being formed between successivethrough-bores 30. FIG. 7 shows, corresponding to FIG. 3, a control diskwith a recess 31′ which, with the opposite recess, forms a channel whosecross section corresponds to that of the though-bores 30 and whichextends over an angle range of about 45°. However, this recess 31′ canalso extend over a greater angle range.

Moreover, in an embodiment of the control disks according to FIG. 7,throttle positions can be formed by means of the opposite recesses 31′overlapping only at the ends. For this purpose, instead of having therounded configuration, the ends can also taper to a point. In such anembodiment, the volume between the throttle positions is increased bythe extension of the recesses in the circumferential direction towardthe through-bore 30.

As has already been stated, this channel extending through theoverlapping recesses 31′ in the circumferential direction can have aflow cross section corresponding to that of the through-bores 30, forexample for highly viscous fluids such as adhesives and the like.However, it is also possible for these recesses 31′ to be designedtapering over a shorter circumferential section than that shown, sothat, when the recesses 31′ overlap, a connection channel tapering inthe flow cross section is obtained between the through-bores 30. In sucha design, for example, the recess 31 shown in FIG. 3 extends over abouta quarter of a circle instead of a semicircle.

In addition, the flow cross section formed by the recesses 31 can alsobe changed by means of the shape of the recess 31 changing about thecircumference, for example by means of the recesses 31 which extend inthe circumferential direction having indents, or bulges projecting intothe recess, presenting obstacles or cross-sectional changes in thechannel formed through the overlapping recesses 31, so that a certainmixing action in the fluid flowing through the device is also produced.

In the flow control device described, the diameter of the through-bores30 is, for example, 5 mm. However, larger flow cross sections can alsobe provided in such a flow control device.

1. A flow control device, comprising at least three control disks whichare arranged coaxially with respect to one another and lie tightlyagainst one another, from which the control disk lying betweenstationary control disks can rotate through an actuating device, thecontrol disks having a through-bore arranged eccentrically and leadingthrough in the axial direction, and, on the side faces lying against oneanother, in each case a recess which, starting from the through-boreextends along an arc of a circle about the axis of the control disks, sothat if the control disks rotate relatively toward each other, onlyparts of the opposite recess overlap.
 2. The flow control device asclaimed in claim 1, in which the recesses formed on opposite side facesof the control disks extend in the opposite direction in thecircumferential direction, starting from the through-bore.
 3. The flowcontrol device as claimed in claim 1, in which the width and depth ofthe recesses taper to approximately zero starting from the through-bore.4. The flow control device as claimed in claim 1, in which rotatable andstationary control disks are arranged alternately between stationary enddisks, and the stationary control disks arranged between the end disks,and the rotatable control disks each have a recess in the form of an arcof a circle on both side faces.
 5. The flow control device as claimed inclaim 4, in which the stationary control disks are fixed on a shaftpassing through them, whereas the rotatable control disks have, on theouter circumference, an engagement means for a rotary drive mechanism.6. The flow control device as claimed in claim 5, in which the rotatablecontrol disks have, on the outer circumference, wedge-shaped centeringgrooves into which centering grub screws engage free from play, thesebeing guided through a rotatable sleeve which surrounds the controldisks.
 7. The flow control device as claimed in claim 6, in which thesleeve on the outer circumference surrounding the control disks isprovided with a worm thread with which a worm, set in rotation by adrive motor, is in engagement.
 8. The flow control device as claimed inclaim 1, in which the control disks are arranged in a two-part housing,both parts of which are clamped together by a screw-on sleeve.
 9. Theflow control device as claimed in claim 1, in which the control disksare held lying against one another in the axial direction by a spring.